This invention pertains in general to processes for manufacturing semiconductor devices and in particular to a process for cleaning the surfaces of laser scribed semiconductor die.
A fundamental operation in the manufacture of semiconductor devices is the procedure by which the semiconductor units which have been batch fabricated on a semiconductor wafer are separated into individual, separate units commonly referred to as chips or die. Traditionally this separation was performed by scribing the surface of the semiconductor wafer to form a rectangular grid such that each rectangle delineated the periphery of a particular semiconductor unit. Application of mechanical pressure to the surface of the wafer caused fracturing along the scribed lines to accomplish the separation into individual semiconductor units or die. One problem inherent in a "scribe and break" operation of this type is the tendency for a semiconductor wafer to fracture along the natural cleavage planes associated with its crystal structure. This sometimes caused fracturing which did not correspond to the scribe rectangular grid such that some die were ruined. A recent improvement which alleviated this problem was the adoption of laser "scribing" in which a laser beam is used to melt narrow channels into the surface of the semiconductor wafer corresponding to the rectangular grid defining the periphery of the semiconductor die. The energy of the laser beam can be adjusted to form a channel which is relatively deep such that the resulting breaking operation will correspond to the rectangular grid rather than to crystal cleavage plains. Although the use of laser scribing offers definite advantages over diamond scribing, it introduces a new problem. This problem arises because relatively large volumes of oxide and silicon are melted by the laser beam as it cuts a channel along the scribe grid and this molten material is spewed out on either side of the channel as slag and debris. Secondary melting causes the slag to adhere firmly to the surface of the semiconductor die making it difficult to remove. The presence of laser slag on the surfaces of the semiconductor die can interfere mechanically to affect the yield of subsequent bonding steps in the assembly of the semiconductor die into a completed semiconductor device. The slag can also interfere electrically to form shorts and leakage paths which affect the electrical quality of the completed semiconductor device.